Regional Security Officer (RSO) is the title given to a special agent of the U.S. Diplomatic Security Service (DSS) who is in charge of a Regional Security Office. The RSO is the principal security attaché and advisor to the U.S. Ambassador at American embassies and consulates. Working for the United States Department of State as special agents, RSOs are also considered to be officers of the State Department acting as specialists within the United States Foreign Service. The RSO is also the senior law enforcement representative at a U.S. Embassy.